Hemostatic wound dressings and methods of making same

ABSTRACT

The present invention is directed to a hemostatic wound dressing that utilizes a fibrous, fabric substrate made from carboxylic-oxidized cellulose and containing a first surface and a second surface opposing the first surface, the fabric having flexibility, strength and porosity effective for use as a hemostat; and further having a porous, polymeric matrix substantially homogeneously distributed on the first and second surfaces and through the fabric, the porous, polymeric matrix being made of a biocompatible, water-soluble or water-swellable cellulose polymer, wherein prior to distribution of the polymeric matrix on and through the fabric, the fabric contains about 3 percent by weight or more of water-soluble oligosaccharides.

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/186,021, filed Jun. 28, 2002, U.S. patent application SerNo. 10/304,781, filed Nov. 26, 2002, now abandoned U.S. patentapplication Ser. No. 10/305,040, filed Nov. 26, 2002, now abandoned U.S.patent application Ser. No. 10/304,472, filed Nov. 26, 2002 nowabandoned, and U.S. patent application Ser. No. 10/326,244, filed Dec.20, 2002.

FIELD OF THE INVENTION

The present invention relates to hemostatic wound dressings containing afabric substrate and a porous, water-soluble or water-swellablepolymeric matrix disposed on and through the substrate and to methods ofmaking such hemostatic wound dressings.

BACKGROUND OF THE INVENTION

The control of bleeding is essential and critical in surgical proceduresto minimize blood loss, to reduce post-surgical complications, and toshorten the duration of the surgery in the operating room. Due to itsbiodegradability and its bactericidal and hemostatic properties,cellulose that has been oxidized to contain carboxylic acid moieties,hereinafter referred to as carboxylic-oxidized cellulose, has long beenused as a topical hemostatic wound dressing in a variety of surgicalprocedures, including neurosurgery, abdominal surgery, cardiovascularsurgery, thoracic surgery, head and neck surgery, pelvic surgery andskin and subcutaneous tissue procedures.

Currently utilized hemostatic wound dressings include knitted ornon-woven fabrics comprising carboxylic-oxidized cellulose. Currentlyutilized oxidized regenerated cellulose is carboxylic-oxidized cellulosecomprising reactive carboxylic acid groups and which has been treated toincrease homogeneity of the cellulose fiber. Examples of such hemostaticwound dressings commercially available include Surgicel® absorbablehemostat; Surgicel Nu-Knit® absorbable hemostat; and Surgicel® Fibrillarabsorbable hemostat; all available from Johnson & Johnson WoundManagement Worldwide, a division of Ethicon, Inc., Somerville, N.J., aJohnson & Johnson Company. Other examples of commercial absorbablehemostats containing carboxylic-oxidized cellulose include Oxycel®absorbable cellulose surgical dressing from Becton Dickinson andCompany, Morris Plains, N.J. The oxidized cellulose hemostats notedabove are knitted fabrics having a porous structure effective forproviding hemostasis. They exhibit good tensile and compressive strengthand are flexible such that a physician can effectively place thehemostat in position and maneuver the dressing during the particularprocedure being performed.

Wound dressings utilizing carboxylic-oxidized cellulose, due to itsacidic pH, are known to rapidly denature acid-sensitive, hemostaticproteins, including thrombin or fibrinogen, on contact. Thus, it isproblematic to use the carboxylic-oxidized cellulose as a carrier foracid-sensitive species, such as thrombin and fibrinogen, as well asother acid-sensitive biologics and pharmaceutical agents.

In addition to issues concerning compatibility of conventionalcarboxylic-oxidized cellulose with “acid-sensitive” species, e.g.proteins, drugs, etc., while the absorbency of body fluid and thehemostatic action of such currently available carboxylic-oxidizedcellulose hemostats are adequate for applications where mild to moderatebleeding is encountered, they are not known to be effective to provideand maintain hemostasis in cases of severe bleeding where a relativelyhigh volume of blood is lost at a relatively high rate. In suchinstances, e.g. arterial puncture, liver resection, blunt liver trauma,blunt spleen trauma, aortic aneurysm, bleeding from patients withover-anticoagulation, or patients with coagulopathies, such ashemophilia, etc., a higher degree of hemostasis is required quickly.

In an effort to achieve enhanced hemostatic properties, blood-clottingagents, such as thrombin, fibrin and fibrinogen have been combined withother carriers or substrates for such agents, including gelatin-basedcarriers and a collagen matrix. Hemostatic wound dressings containingneutralized carboxylic-oxidized cellulose and protein-based hemostaticagents, such as thrombin, fibrinogen and fibrin are known. Neutralizedcarboxylic-oxidized cellulose is prepared by treating thecarboxylic-oxidized cellulose with a water solution or alcohol solutionof a basic salt of a weak organic acid to elevate the pH of thecarboxylic-oxidized cellulose to between 5 and 8 by neutralizing theacid groups on the cellulose prior to addition of thrombin in order tomake it thrombin-compatible. While such neutralized cellulose may bethrombin compatible, it is no longer bactericidal, as the anti-microbialactivity of the carboxylic-oxidized cellulose provided by its acidicnature is lost.

Hemostatic agents such as thrombin, fibrinogen or fibrin, if noteffectively bound chemically or physically to the substrate, may berinsed away by blood at a wound site. The unbound agent may migrate intothe blood stream, which is undesired. Methods of producing highlyoxidized tri-carboxylic acid derivatives of cellulose as hemostaticmaterials, involving two-stage oxidation by successive processing withan iodine-containing compound and nitrogen oxides, has been disclosed inRU2146264 and IN159322. As disclosed in these disclosures, oxidizedcellulosic materials were prepared by preliminary oxidation withmetaperiodate or periodic acid to yield periodate-oxidized, dialdehydecellulose to form the intermediate for forming carboxylic-oxidizedcellulose. The dialdehyde cellulose intermediate then is furtheroxidized by NO₂ to yield the carboxylic-oxidized cellulose, which thenis used as a hemostatic, anti-microbial and wound-healing agent.

It would be advantageous to provide a hemostatic wound dressing that notonly provides hemostasis and anti-microbial properties similar to orbetter than conventional carboxylic-oxidized cellulose-containinghemostatic wound dressings and that also is compatible with“acid-sensitive” species, but that does so without the risk ofhemostatic agents migrating into the blood stream.

It also would be advantageous to provide hemostatic wound dressings thatprovide and maintain hemostasis in cases of severe bleeding and thatmaintain physical properties required for use as a wound dressing,including strength and flexibility necessary for placement andmaneuvering in or on the body by a physician. It also would beadvantageous to provide methods of making such wound dressings thatenable efficient and economic production of such dressings, such thatthe dressings may be manufactured on a commercial scale.

The present invention provides wound dressings that provide hemostaticand anti-microbial properties equivalent to or better than conventionalcarboxylic-oxidized cellulose-based hemostatic wound dressings, and/orthat also may be compatible with “acid-sensitive” species, and improvedmethods for preparing such wound dressings.

SUMMARY OF THE INVENTION

The present invention is directed to hemostatic wound dressingscomprising a fabric substrate, said fabric substrate comprising a firstsurface and a second surface opposing said first surface, said fabricsubstrate comprising fibers and having flexibility, strength andporosity effective for use as a hemostat, said fabric comprisingbiocompatible carboxylic-oxidized cellulose; and a porous, polymericmatrix substantially homogeneously distributed on said first surface andsaid second surface and through said fabric substrate, said porous,polymeric matrix comprising a biocompatible, water-soluble orwater-swellable cellulose polymer, wherein prior to distribution of saidpolymeric matrix on and through said fabric substrate, said fabricsubstrate comprises about 3 percent by weight or more of water-solubleoligosaccharides; and to methods of making such wound dressings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a scanning electron microscopy image (×75) of a cross sectionof a comparative wound dressing.

FIG. 2 is a scanning electron microscopy image (×75) of the firstsurface of a comparative wound dressing.

FIG. 3 is a scanning electron microscopy image (×75) of a cross sectionof a comparative wound dressing.

FIG. 4 is a scanning electron microscopy image (×75) of the firstsurface of a comparative wound dressing.

FIG. 5 is a scanning electron microscopy image (×75) of the secondopposing surface of a comparative wound dressing.

FIG. 6 is a scanning electron microscopy image (×75) of a cross-sectionof a wound dressing of the present invention.

FIG. 7 is a scanning electron microscopy image (×150) of a cross-sectionof a wound dressing of the present invention.

FIG. 8 is a scanning electron microscopy image (×75) of the firstsurface of a wound dressing of the present invention.

FIG. 9 is a scanning electron microscopy image (×75) of the secondopposing surface of a wound dressing of the present invention.

FIG. 10 is a scanning electron microscopy image (×75) of a cross-sectionof a wound dressing of the present invention.

FIG. 11 is a scanning electron microscopy image (×75) of the firstsurface of a wound dressing of the present invention.

FIG. 12 is a scanning electron microscopy image (×75) of the secondopposing surface of a wound dressing of the present invention.

FIG. 13 is a top plan view of the transfer of the saturated fabric fromthe polymer solution to a transfer support means.

FIG. 14 is an elevational side view of the transfer of the saturatedfabric from the polymer solution to a transfer support means.

FIG. 15 is an elevational side view of the transfer of the saturatedfabric from the polymer solution to a transfer support means.

FIG. 16 a is a plan view of the first surface of a wound dressingprepared according to the method of the present invention.

FIG. 16 b is a plan view of the second surface of a wound dressingprepared according to the method of the present invention.

FIG. 16 c is an enlarged fragmentary side view as seen along view line16C-16C of a wound dressing prepared according to the method of thepresent invention.

FIG. 17 a is a plan view of the first surface of a wound dressingprepared by a comparative method.

FIG. 17 b is a plan view of the second surface of a wound dressingprepared by a comparative method.

FIG. 17 c is enlarged fragmentary side view as seen along view line17C-17C of a wound dressing prepared by a comparative method.

FIG. 18 a is plan view of the first surface of a wound dressing preparedby a comparative method.

FIG. 18 b is a plan view of the second surface of a wound dressingprepared by a comparative method.

FIG. 18 c is an enlarged fragmentary side view as seen along view line18C-18C of a wound dressing prepared by a comparative method.

FIG. 19 a is a plan view of the first surface of a comparative wounddressing.

FIG. 19 b is a plan view of the first surface of a comparative wounddressing.

FIG. 19 c is an enlarged fragmentary side view as seen along view line19C-19C view of a comparative wound dressing.

FIG. 20 is a plan view of the surface of a fabric containing wounddressings of the present invention.

FIG. 21 is a perspective view of a discrete element of a wound dressingof the present invention as shown in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

We have discovered certain hemostatic wound dressings that utilize afabric as a substrate, where the fabric substrate comprises fibersprepared from a biocompatible polymer(s), comprises a first surface, asecond surface opposing the first surface, and that possesses propertiessuitable for use as a hemostat, e.g. strength, flexibility and porosity.A more detailed description of such fabric properties is presentedherein below. The wound dressings further comprise a porous, polymericmatrix substantially homogeneously dispersed on the first and secondsurfaces and through the fabric substrate. Either of the first andsecond surfaces may be used to contact the wound. The hemostatic wounddressings of the present invention provide and maintain effectivehemostasis when applied to a wound requiring hemostasis. Effectivehemostasis, as used herein, is the ability to control and/or abatecapillary, venous, or arteriole bleeding within an effective time, asrecognized by those skilled in the art of hemostasis. Furtherindications of effective hemostasis may be provided by governmentalregulatory standards and the like.

Fabrics utilized in conventional hemostatic wound dressings, such asSurgicel® absorbable hemostat; Surgicel Nu-Knit® absorbable hemostat;and Surgicel® Fibrillar absorbable hemostat; all available from Johnson& Johnson Wound Management Worldwide, a division of Ethicon, Inc.,Somerville, N.J., a Johnson & Johnson Company, as well as Oxycel®absorbable cellulose surgical dressing from Becton Dickinson andCompany, Morris Plains, N.J., all may be used in preparing wounddressings according to the present invention. In certain embodiments,wound dressings of the present invention are effective in providing andmaintaining hemostasis in cases of severe bleeding. As used herein,severe bleeding is meant to include those cases of bleeding where arelatively high volume of blood is lost at a relatively high rate.Examples of severe bleeding include, without limitation, bleeding due toarterial puncture, liver resection, blunt liver trauma, blunt spleentrauma, aortic aneurysm, bleeding from patients withover-anticoagulation, or bleeding from patients with coagulopathies,such as hemophilia. Such wound dressings allow a patient to ambulatequicker than the current standard of care following, e.g. a diagnosticor interventional endovascular procedure.

In certain embodiments of the invention, the wound dressings may furtherinclude a hemostatic agent, or other biological or therapeuticcompounds, moieties or species, including drugs and pharmaceuticalagents as described in more detail herein below. The agents may be boundwithin the polymeric matrix, as well as to the fabric surfaces and/orwithin the fabric. The agents may be bound by chemical or physicalmeans, provided that they are bound such that they do not migrate fromthe wound dressing upon contact with blood in the body. The hemostaticagent may be dispersed partially or homogenously through the fabricand/or the polymeric matrix. In some embodiments of the invention, thehemostatic agents, or other biological or therapeutic compounds,moieties or species, e.g. drugs, and pharmaceutical agents, may be“acid-sensitive”, meaning that they may be degraded or denatured by, orotherwise detrimentally affected by acidic pH, such as is provided byconventional carboxylic-oxidized hemostatic wound dressings.

The fabric substrates utilized in the present invention may be woven ornonwoven, provided that the fabric possesses the physical propertiesnecessary for use in hemostatic wound dressings. A preferred wovenfabric has a dense, knitted structure that provides form and shape forthe hemostatic wound dressings. Such fabrics are described in U.S. Pat.No. 4,626,253, the contents of which is hereby incorporated by referenceherein as if set forth in its entirety.

In preferred embodiments of the present invention, the absorbablehemostatic fabrics are warp knitted tricot fabrics constructed of brightrayon yarn which is subsequently oxidized to include carboxyl oraldehyde moieties in amounts effective to provide the fabrics withbiodegradability and anti-microbial activity. The fabrics arecharacterized by having a single ply thickness of at least about 0.5 mm,a density of at least about 0.03 g/cm², air porosity of less than about150 cm³/sec/cm², and liquid absorption capacity of at least about 3times the dry weight of the fabric and at least about 0.1 g water percm² of the fabric.

The knitted fabrics have good bulk without undue weight, are soft anddrapable, and conform well to the configuration of the surface to whichthey are applied. The fabric may be cut into suitable sizes and shapeswithout running or fraying along the cut edge. Fabric strength afteroxidation is adequate for use as a surgical hemostat.

Preferred hemostatic fabrics used in the present invention compriseoxidized cellulose and are best characterized by their physicalproperties of thickness, bulk, porosity and liquid absorption capacity,as recited above. Suitable fabrics having these properties may beconstructed by knitting 60 denier, 18-filament bright rayon yarn on a32-gauge machine at a knit quality of 12. A suitable tricot fabricconstruction is front-bar 1-0, 10-11; back-bar 2-3, 1-0. The extendedshog movement imparted to the front bar results in a 188 inch runnercompared to a 70 inch runner for the back guide bar, and increases thefabric bulk and density. The ratio of front to back bar runners in thisparticular construction is 1:2.7.

Typical physical and hemostatic properties of preferred fabrics producedas described above are noted in Table 1.

TABLE I Property Thickness (mm); 0.645 Density (g/cm²); 0.052 AirPorosity (cm³/sec/cm²); 62.8 Tensile Strength⁽¹⁾ (md/cd)Kg; 1.9/4.5Elongation⁽²⁾ (%); 23/49 Absorption⁽³⁾ (g/g fabric); 3.88 (g/cm²fabric); 0.20 Hemostasis⁽⁴⁾ (min) 1 ply; 5.7 ± 1.0 2 ply; 5.6 ± 1.8⁽¹⁾tensile strength determined at 2 in/min extension md/cd = machinedirection/cross direction. ⁽²⁾Elongation, machine direction/crossdirection. ⁽³⁾Absorption based on weight of water absorbed by fabric.⁽⁴⁾Hemostasis evaluation on incised porcine splenic wounds, time to stopbleeding.

The tricot fabrics utilized in the present invention may be constructedfrom bright rayon yarns of from about 40 to 80 total denier. Each yarnmay contain from 10 to 25 individual filaments, although each individualfilament preferably is less than 5 denier to avoid extended absorptiontimes. The high bulk and fabric density are obtained by knitting at 28gauge or finer, preferably at 32 gauge, with a fabric quality of about10 or 12 (40 to 48 courses per inch). A long guide bar shog movement ofat least 6 needle spaces, and preferably 8 to 12 spaces, furtherincreases fabric thickness and density.

Other warp knit tricot fabric constructions which produce equivalentphysical properties may, of course, be utilized in the manufacture ofthe improved hemostatic fabrics and wound dressings of the presentinvention, and such constructions will be apparent to those skilled inthe art.

Polymers useful in preparing the fabric substrates in wound dressings ofthe present invention include, without limitation, collagen, calciumalginate, chitin, polyester, polypropylene, polysaccharides, polyacrylicacids, polymethacrylic acids, polyamines, polyimines, polyamides,polyesters, polyethers, polynucleotides, polynucleic acids,polypeptides, proteins, poly (alkylene oxide), polyalkylenes,polythioesters, polythioethers, polyvinyls, polymers comprising lipids,and mixtures thereof. Preferred fibers comprise oxidized regeneratedpolysaccharides, in particular oxidized regenerated cellulose.

Preferably, oxidized polysaccharides are used to prepare wound dressingsof the present invention. More preferably, oxizided cellulose is used toprepare fabrics used in wound dressings of the present invention. Thecellulose either may be carboxylic-oxidized cellulose, or may bealdehyde-oxidized cellulose, each as defined and described herein. Evenmore preferably, oxidized regenerated cellulose is used to preparefabric substrates used in wound dressings of the present invention.Regenerated cellulose is preferred due to its higher degree ofuniformity versus cellulose that has not been regenerated. Regeneratedcellulose and a detailed description of how to make regenerated oxidizedcellulose is set forth in U.S. Pat. No. 3,364,200 and U.S. Pat. No.5,180,398, the contents each of which is hereby incorporated byreference as if set forth in its entirety. As such, teachings concerningregenerated oxidized cellulose and methods of making same are wellwithin the knowledge of one skilled in the art of hemostatic wounddressings.

Certain of the wound dressings of the present invention utilize fabricsubstrates that have been oxidized to contain carboxyl moieties inamounts effective to provide the fabrics with biodegradability andanti-microbial activity. U.S. Pat. 3,364,200 discloses the preparationof carboxylic-oxidized cellulose with an oxidizing agent such asdinitrogen tetroxide in a Freon medium. U.S. Pat. No. 5,180,398discloses the preparation of carboxylic-oxidized cellulose with anoxidizing agent such as nitrogen dioxide in a per-fluorocarbon solvent.After oxidation by either method, the fabric is thoroughly washed with asolvent such as carbon tetrachloride, followed by aqueous solution of 50percent isopropyl alcohol (IPA), and finally with 99% IPA. Prior tooxidation, the fabric is constructed in the desired woven or nonwovenconstruct suitable for use as a hemostat. Certain wound dressingsaccording to the present invention that utilize such fabrics have beenfound to provide and maintain hemostasis in cases of severe bleeding.

Where the fabric substrate comprises carboxylic-oxidized cellulose, ithas been found that the fabric preferably is conditioned prior tosaturation with polymer solution and lyophilization in order to providehomogenous distribution of the polymer solution on and through thefabric substrate. Conditioning of the fabric can be achieved by storingthe fabric at room temperature under ambient conditions for at least 6months, or conditioning of the fabric can be accelerated. Preferably,the fabric is exposed to conditions of about 4° C. to about 90° C., at arelative humidity of from about 5% to about 90%, for a time of fromabout 1 hour to 48 months. More preferably, the fabric is exposed toconditions of about 4° C. to about 60° C., at a relative humidity offrom about 30% to about 90%, for a time of from about 72 hours to 48months. Even more preferably, the fabric is exposed to conditions ofabout 18° C. to about 50° C., at a relative humidity of from about 60%to about 80%, for a time of from about 72 hours to 366 hours. Mostpreferably, the fabric is conditioned at a temperature of about 50° C.,at a relative humidity of about 70%, for a time of about 168 hours. Thefabric may be placed horizontally in a conditioned environment, takingcare to provide spacing between the fabric substrates to allow properconditioning. The fabric also may be suspended vertically to allowconditioning.

As result of the conditioning of the carboxylic-oxidized cellulosefabric substrate, the fabric substrate will comprise at least about 3weight percent of water-soluble molecules, preferably from about 3 toabout 30 weight percent, more preferably from about 8 to about 20 weightpercent, even more preferably from about 9 to about 12 weight percent,and most preferably about 10 weight percent. In general, thewater-soluble molecules are acid-substituted oligosaccharides containingapproximately 5 or fewer saccharide rings. It has been found that thehemostatic efficacy of the wound dressing containing suchcarboxylic-oxidized cellulose fabric substrates, including theoccurrence of re-bleeding of a wound for which hemostasis initially hasbeen achieved, is improved when the contents of the water-solublemolecules reach about 8%, preferably about 10%, based on the weight ofthe fabric substrate.

Fabric substrates used in the present invention also will comprise fromabout 3 to about 20 weight percent of water, preferably from about 7 toabout 13 weight percent, and more preferably from about 9 to about 12weight percent water.

Similar levels of moisture and water-soluble molecules in thecarboxylic-oxidized cellulose fabric substrate also may be achieved byother means. For example, sterilization of the fabric by knowtechniques, such as gamma or e-beam irradiation, may provide similarcontent of water and/or water-soluble molecules. In addition,water-soluble molecules such as oligosacchrides could be added to thefabric prior to distribution of the porous, polymeric matrix on andthrough the fabric. Once having the benefit of this disclosure, thoseskilled in the art may readily ascertain other methods for providingsuch fabrics with moisture and/or water-soluble molecules.

Wound dressings of the present invention that are compatible withacid-sensitive species comprise fabric substrates prepared from abiocompatible, aldehyde-oxidized polysaccharide. In such wounddressings, the polysaccharide preferably will contain an amount ofaldehyde moieties effective to render the modified polysaccharidebiodegradable, meaning that the polysaccharide is degradable by the bodyinto components that either are resorbable by the body, or that can bepassed readily by the body. More particularly, the biodegradedcomponents do not elicit permanent chronic foreign body reaction whenthey are absorbed by the body, such that no permanent trace or residualof the component is retained at the implantation site.

Aldehyde-oxidized polysaccharides used in the present invention mayinclude, without limitation, cellulose, cellulose derivatives, e.g.alkyl cellulose, for instance methyl cellulose, hydroxyalkyl cellulose,alkylhydroxyalkyl cellulose, cellulose sulfate, salts of carboxymethylcellulose, carboxymethyl cellulose and carboxyethyl cellulose, chitin,carboxymethyl chitin, hyaluronic acid, salts of hyaluronic acid,alginate, alginic acid, propylene glycol alginate, glycogen, dextran,dextran sulfate, curdlan, pectin, pullulan, xanthan, chondroitin,chondroitin sulfates, carboxymethyl dextran, carboxymethyl chitosan,heparin, heparin sulfate, heparan, heparan sulfate, dermatan sulfate,keratin sulfate, carrageenans, chitosan, starch, amylose, amylopectin,poly-N-glucosamine, polymannuronic acid, polyglucuronic acid,polyguluronic acid and derivatives of the above, each of which has beenoxidized to included anti-microbial effective amounts of aldehydemoieties.

In preferred embodiments utilizing aldehyde-oxidized polysaccharides,the polysaccharide is oxidized as described herein to assure that thealdehyde-oxidized polysaccharide is biodegradable. Such biodegradable,aldehyde-oxidized polysaccharides may be represented by Structure Ibelow.

where x and y represent mole percent, x plus y equals 100 percent, x isfrom about 95 to about 5, y is from about 5 to about 95; and R may beCH₂OR₃, COOR₄, sulphonic acid, or phosphonic acid; R₃ and R₄ may be H,alkyl, aryl, alkoxy or aryloxy, and R₁ and R₂ may be H, alkyl, aryl,alkoxy, aryloxy, sulphonyl or phosphoryl.

In certain embodiments of the present invention, the biocompatible,biodegradable hemostatic wound dressing comprises a fabric substrateprepared from a biocompatible, biodegradable, aldehyde-oxidizedregenerated cellulose. In particular, preferred aldehyde-oxidizedregenerated cellulose is one comprising repeating units of Structure II:

where x and y represent mole percent, x plus y equals 100 percent, x isfrom about 95 to about 5, y is from about 5 to about 95; and R is CH₂OH,R₁ and R₂ are H.

In preferred embodiments of the invention, the aldehyde-oxidizedregenerated polysaccharide, e.g. cellulose, is essentially free offunctional or reactive moieties other than aldehyde moieties. Byessentially free, it is meant that the polysaccharide does not containsuch functional or reactive moieties in amounts effective to alter theproperties of the aldehyde-oxidized polysaccharide, or to provide thefabric comprising the polysaccharide with a pH of less than about 4.5,more preferably less than about 5, or greater than about 9, preferablyabout 9.5. Such moieties include, without limitation, carboxylic acidmoieties typically present in wound dressings made fromcarboxyl-oxidized cellulose. Excess levels of carboxylic acid moietieswill lower the pH of the fabrics and dressings so that they are notcompatible for use with those acid-sensitive species that may bedegraded or denatured by such a low pH, e.g. thrombin. Other moietiesessentially excluded include, without limitation, sulfonyl or phosphonylmoieties.

As noted above, wound dressings of the present invention comprise aporous, polymeric matrix dispersed substantially homogenously on thefirst and second surfaces and through the fabric substrate. The polymerused to prepare the porous, polymeric matrix in wound dressings of thepresent invention is a biocompatible, water-soluble, or water-swellablepolymer. The water-soluble or water-swellable polymer rapidly absorbsblood or other body fluids and forms a tacky or sticky gel adhered totissue when placed in contact therewith. The fluid-absorbing polymer,when in a dry or concentrated state, interacts with body fluid through ahydration process. Once applied in a bleeding site, the polymerinteracts with the water component in the blood via the hydrationprocess. The hydration force provides an adhesive interaction that aidsthe hemostat adhere to the bleeding site. The adhesion creates a sealinglayer between the hemostat and the bleeding site to stop the blood flow.

Preferred polymers used to fabricate the matrices includepolysaccharides. Such polysaccharides include, without limitation,cellulose, alkyl cellulose, e.g. methylcellulose, alkylhydroxyalkylcellulose, hydroxyalkyl cellulose, cellulose sulfate, salts ofcarboxymethyl cellulose, carboxymethyl cellulose, carboxyethylcellulose, chitin, carboxymethyl chitin, hyaluronic acid, salts ofhyaluronic acid, alginate, alginic acid, propylene glycol alginate,glycogen, dextran, dextran sulfate, curdlan, pectin, pullulan, xanthan,chondroitin, chondroitin sulfates, carboxymethyl dextran, carboxymethylchitosan, chitosan, heparin, heparin sulfate, heparan, heparan sulfate,dermatan sulfate, keratan sulfate, carrageenans, chitosan, starch,amylose, amylopectin, poly-N-glucosamine, polymannuronic acid,polyglucuronic acid polyguluronic acid, and derivatives of any of theabove. The composite hemostat of the present invention remains veryflexible, conforms to a bleeding site and retains good tensile andcompressive strength to withstand handling during application. Thehemostat can be cut into different sizes and shapes to fit the surgicalneeds. It can be rolled up or packed into irregular anatomic areas. Thefabric in a preferred embodiment capable of providing and maintaininghemostasis in cases of severe bleeding is a knitted carboxylic-oxidizedregenerated cellulose, such as the fabric used to manufacture SurgicelNu-Knit® absorbable hemostat available from Ethicon, Inc., Somerville,N.J.

As noted above, in certain embodiments of the invention, a biologics, adrug, a hemostatic agent, a pharmaceutical agent, or combinationsthereof, that otherwise may be sensitive to the low pH of conventionalcarboxyl-oxidized cellulose-containing wound dressings, may beincorporated into wound dressings of the present invention withouthaving to adjust pH prior to incorporation into the dressing. Tofabricate such a hemostatic wound dressing, a drug or agent may bedissolved in an appropriate solvent. The fabric may then be coated withthe drug solution and the solvent removed. Preferred biologics, drugsand agent include analgesics, anti-infective agents, antibiotics,adhesion preventive agents, pro-coagulants, and wound healing growthfactors.

Hemostatic agents that may be used in wound dressings according to thepresent invention include, without limitation, procoagulant enzymes,proteins and peptides, can be naturally occurring, recombinant, orsynthetic, and may be selected from the group consisting of prothrombin,thrombin, fibrinogen, fibrin, fibronectin, heparinase, Factor X/Xa,Factor VII/VIIa, Factor IX/IXa, Factor XI/XIa, Factor XII/XIIa, tissuefactor, batroxobin, ancrod, ecarin, von Willebrand Factor, collagen,elastin, albumin, gelatin, platelet surface glycoproteins, vasopressinand vasopressin analogs, epinephrine, selectin, procoagulant venom,plasminogen activator inhibitor, platelet activating agents, syntheticpeptides having hemostatic activity, derivatives of the above and anycombination thereof. Preferred hemostatic agents used in the presentinvention are thrombin, fibrinogen and fibrin.

Protein-based hemostatic agents, such as thrombin, fibrin or fibrinogen,if bound to the wound dressing, can enhance the hemostatic property ofaldehyde-oxidized regenerated cellulose wound dressings and reduce therisk of thrombosis caused by free hemostatic agents migrating into theblood stream. Hemostatic agents may be bound to the wound dressingseither by chemical of physical means. Agents may be covalentlyconjugated with aldehyde groups pendant from the polysaccharide in oneinstance, thus chemically binding the agent to the wound dressing.Preferably, the hemostatic agents are physically bound to the wounddressing via incorporation into the polymeric matrix dispersed on andthrough the aldehyde-oxidized polysaccharide fabric and immobilized,i.e. bound, via lyophilization.

Such hemostatic wound dressings of the present invention comprisehemostatic agents, including but not limited to thrombin, fibrinogen orfibrin, in an amount effective to provide rapid hemostasis and maintaineffective hemostasis in cases of severe bleeding. If the concentrationof the hemostatic agent in the wound dressing is too low, the hemostaticagent does not provide an effective proagulant activity to promote rapidclot formation upon contact with blood or blood plasma. A preferredconcentration range of thrombin in the wound dressing is from about0.001 to about 1 percent by weight. A more preferred concentration ofthrombin in the wound dressing is from about 0.01 to about 0.1 percentby weight. A preferred concentration range of fibrinogen in the wounddressing is from about 0.1 to about 50 percent by weight. A morepreferred concentration of fibrinogen in the wound dressing is fromabout 2.5 to about 10 by weight. A preferred concentration range offibrin in the wound dressing is from about 0.1 to about 50 percent byweight. A more preferred concentration of fibrin in the wound dressingis from about 2.5 to about 10 by weight.

In certain embodiments, fabrics used in wound dressings of the presentinvention may comprise covalently conjugated there with a hemostaticagent bearing an aldehyde-reactive moiety. In such embodiments, thealdehyde moiety of aldehyde-oxidized regenerated polysaccharide canreadily react with the amine groups present on the amino acid sidechains or N-terminal residues of thrombin, fibrinogen or fibrin,resulting in forming a conjugate of the hemostatic agent with thealdehyde-oxidized regenerated polysaccharide covalently linked by areversible imine bond. The imine bonded aldehyde-oxidized regeneratedpolysaccharide/hemostatic agent conjugate may then be further reactedwith a reducing agent such as sodium borohydride or sodiumcyanoborohydride to form an irreversible secondary amine linkage. Insuch embodiments of the invention, the hemostatic agent is dispersed atleast on the surface of the fabric, and preferably at least partiallythrough the fabric structure, bound reversibly or irreversibly to thealdehyde-oxidized polysaccharide.

Oxidation of 2,3-vicinal hydroxyl groups in a carbohydrate with periodicacid (or any alkali metal salt thereof) forms a di-aldehyde ordi-aldehyde derivatives. These aldehyde moieties(—RCH(O)) can thenreadily react with a primary amine moiety (—NH₂), such as are present onthe amino acid side chains or N-terminal residues of proteins, resultingin an equilibrium with the reaction product, a protein and carbohydrateconjugate, covalently linked by a relatively unstable and reversibleimine moiety (—N═CHR). To stabilize the linkage between the biomoleculeand the substrate surface, subsequent reductive alkylation of the iminemoiety is carried out using reducing agents (i.e., stabilizing agents)such as, for example, sodium borohydride, sodium cyanoborohydride, andamine boranes, to form a secondary amine (—NH—CH₂—R). The features ofsuch hemostatic agents conjugated with the aldehyde-oxidized regeneratedcellulose wound dressing can be controlled to suit a desired applicationby choosing the conditions to form the composite hemostat duringconjugation.

In such embodiments of the present invention, the hemostatic agent, suchas thrombin, fibrinogen or fibrin, is dispersed substantiallyhomogeneously through the wound dressing fabric. In such cases,aldehyde-oxidized regenerated cellulose fabric may be immersed in thesolution of thrombin, fibrinogen or fibrin to provide homogeneousdistribution throughout the wound dressing.

In certain embodiments of the invention, the thrombin conjugate ofaldehyde-oxidized regenerated cellulose fabric is further reacted withreducing agents such as sodium borohydride or sodium cyanoborohydride toform a secondary amine linkage. The aldehyde-oxidized regeneratedcellulose fabric can be soaked with the desired amount of aqueoussolution of thrombin, then reacted with aqueous solution of sodiumborohydride or sodium cyanoborohydride reconstituted in phosphate buffer(PH═8) prior to lyophilization.

The reduced form of the aldehyde-oxidized regenerated cellulose-thrombinconjugate is more stable due to the nature of the secondary aminelinkage. Hemostatic wound dressings of this embodiment have enhancedhemostatic properties, as well as increased stability, and can providerapid hemostasis without causing thrombin to migrate into the bloodstream and cause severe thrombosis.

In preferred embodiments of the present invention, the hemostatic agent,such as thrombin, fibrinogen, or fibrin is constituted in an aqueoussolution of a non-acidic, water-soluble or water-swellable polymer, asdescribed herein above, including but not limited to methyl cellulose,hydroxyalkyl cellulose, water-soluble chitosan, salts of carboxymethylcarboxyethyl cellulose, chitin, salts of hyaluronic acid, alginate,propylene glycol alginate, glycogen, dextran, carrageenans, chitosan,starch, amylose, poly-N-glucosamine, and the aldehyde-oxidizedderivatives thereof. The aldehyde-oxidized regenerated cellulose fabriccan be soaked with the desired amount of aqueous solution of hemostaticagent and the water-soluble or water-swellable polymer and rapidlylyophilized using known methods that retain therapeutic activity. Whenconstructed thusly, the hemostatic agent will be substantiallyhomogenously dispersed through the polymeric matrix formed duringlyophilization.

One skilled in the art, once having the benefit of this disclosure, willbe able to select the appropriate hemostatic agent, water-soluble orwater-swellable polymer and solvent therefore, and levels of use of boththe polymer and hemostatic agent, depending on the particularcircumstances and properties required of the particular wound dressing.

One method of making the porous, polymeric matrix is to contact thefabric substrate with the appropriate amount of polymer solution, suchthat the dissolved polymer is disposed on the surfaces and substantiallyhomogenously through the fabric, flash-freeze the polymer and fabric,and then remove the solvent from the frozen structure under vacuum, i.e.by lyophilization. The steps involved in the preparation of the novelporous structure comprise dissolving the appropriate polymer to belyophilized in an appropriate solvent for the polymer to prepare ahomogenous polymer solution. The fabric then is contacted with thepolymer solution such that it is saturated with the polymer solution.The fabric substrate and polymer solution incorporated in the denseconstruct of the fabric then is subjected to a freezing and vacuumdrying cycle. The freezing/drying step phase removes the solvent bysublimation, leaving a porous, polymer matrix structure disposed on andthrough the fabric substrate. Through this preferred lyophilizationmethod, the wound dressing comprising a fabric substrate that comprisesa matrix of the water-soluble or water-swellable polymer and havingmicroporous and/or nanoporous structure is obtained. The lyophilizationconditions are important to the novel porous structure in order tocreate a large matrix surface area in the hemostat with which bodyfluids can interact once the dressing is applied to a wound requiringhemostasis.

During the lyophilization process, several parameters and procedures areimportant to produce wound dressings having mechanical propertiessuitable for use in hemostatic wound dressings. The features of suchmicroporous structure can be controlled to suit a desired application bychoosing the appropriate conditions to form the composite hemostatduring lyophilization. The type of microporous morphology developedduring the lyophilization is a function of such factors, such as thesolution thermodynamics, freezing rate, temperature to which it isfrozen, and concentration of the solution. To maximize the surface areaof the porous matrix of the present invention, a preferred method is toquickly freeze the fabric/polymer construct at lower than 0° C.,preferably at about −50° C., and to remove the solvent under highvacuum. The porous matrix produced thereby provides a largefluid-absorbing capacity to the hemostatic wound dressing. When thehemostatic wound dressing comes into contact with body fluid, a verylarge surface area of polymer is exposed to the fluid instantly. Thehydration force of the hemostat and subsequent formation of a tackygelatinous layer helps to create an adhesive interaction between thehemostat and the bleeding site. The microporous structure of thepolymeric matrix also allows blood to quickly pass through the fabricsurface before the hydration takes place, thus providing an increasedamount of the polymer to come in contact with the body fluids. Theformation of a gelatinous sheet on oxidized cellulose upon blood contactwill enhance the sealing property of the water-soluble gelatinous layer,which is critical to rapid hemostasis in cases ranging from moderate tosevere bleeding.

The fabric substrate comprises the polymeric matrix in an amounteffective to provide and maintain effective hemostasis, preferably incases of severe bleeding. If the ratio of polymer to fabric is too low,the polymer does not provide an effective seal to physically block thebleeding, thus reducing the hemostatic properties. If the ratio is toohigh, the composite hemostat wound dressing will be too stiff or toobrittle to conform to wound tissue in surgical applications, thusadversely affecting the mechanical properties necessary for handling bythe physician in placement and manipulation of the dressing. Such anexcessive ratio will also prevent the blood from quickly passing throughthe fabric surface to form the gelatinous layer on the oxidizedcellulose that is critical for enhancing the sealing property. Apreferred weight ratio of polymer to fabric is from about 1:99 to about15:85. A more preferred weight ratio of polymer to fabric is from about3:97 to about 10:90.

Wound dressings of the present invention are best exemplified in thefigures prepared by scanning electron microscope. The samples wereprepared by cutting 1-cm² sections of the dressings by using a razor.Micrographs of both the first surface and opposing second surface, andcross-sections were prepared and mounted on carbon stubs using carbonpaint. The samples were gold-sputtered and examined by scanning electronmicroscopy (SEM) under high vacuum at 4 KV.

FIG. 1 is a cross-section view (75×) of uncoated carboxylic-oxidizedregenerated cellulose fibers 12 organized as fiber bundles 14 andknitted into fabric 10 according to preferred embodiments of theinvention discussed herein above. One commercial example of such afabric is Surgicel Nu-Knit® absorbable hemostatic wound dressing.

FIG. 2 is a view of a first surface of the fabric of FIG. 1. Individualfibers 12 are shown within a bundle.

FIG. 3 is a cross-section view of fabric 20 having first surface 22 andopposing surface 24 and that has been coated with a solution of sodiumcarboxymethyl cellulose (Na—CMC) and then air dried as in Example 6.Individual fibers 23 also are shown.

FIG. 4 is a view of surface 22 of fabric 20. As observed therein, in thecourse of air-drying, polymer 26 agglomerates and adheres to fibers 23,in many instances adhering fibers 23 one to the other and creating largevoids 28 in the hemostatic fabric through which body fluids may pass.Polymer 26 dispersed on and through fabric 20 is not in the state of aporous matrix and thus provides no hemostasis in cases of severebleeding as described herein above due, at least in part, to a lack ofsufficient porosity, e.g. surface area, to provide polymer/body fluidinteraction effective to provide and maintain hemostasis in cases ofsevere bleeding.

FIG. 5 is a view of opposing surface 24 of fabric 20. As shown, opposingsurface 24 contains a larger concentration of Na—CMC coating material asopposed to surface 22 shown in FIG. 4, obscuring most of fibers 23,although the knitting pattern could still be discerned. The coating wasthick enough to span across all of the fibers and generate an intactlayer 27 of its own, also shown in FIG. 3. This layer appeared to bebrittle, as cracks 29 in the coating were observed. The coating layerthickness varied from as thin as about 3 microns in some sections toabout 30-65 microns in other sections.

In comparing the surface morphologies of surface 22 and opposing surface24 of fabric 20, it is apparent that surface 22 contained significantlyless Na—CMC. The coating was significantly thinner on the fibers thanthe coating on the opposing surface. While some Na—CMC was observed tospan across some fibers, the coating was incomplete or had perforationspresent. The coating layer thickness, where present, did not exceedabout 2 microns.

It is clear from FIGS. 3-5 that the fabrics prepared by air-drying donot contain a porous, polymeric matrix homogenously dispersed on thesurfaces and there through. As such, those fabrics do not provide andmaintain hemostasis in cases of severe bleeding, as shown herein. Inaddition, such fabrics are brittle, stiff, do not conform to woundsites, are not able to be handled by physicians, and generally are notsuitable for use as wound dressings in cases of severe bleeding.

Hemostatic fabrics according to the present invention are set forth inFIGS. 6-9. As shown in FIGS. 6 and 7, a porous, polymer matrix is moresubstantially homogenously distributed on surface 32 and throughoutfabric 30. Polymer 36 forms a porous matrix integrated with knittedfibers 33. The porous polymer matrix exhibits significant liquidabsorption properties from capillary action in the same manner as asponge.

As shown in FIGS. 8 and 9, the matrix disposed on the relative surfacescontains countless pores, ranging from about two microns to as large asabout 35 microns in diameter or greater. FIG. 8 shows surface 32 offabric 30. As noted, polymer 36 is present in the form of a porousmatrix about fibers 33, thereby providing ample polymer surface areawith which body fluids can interact upon contact therewith. Opposingsurface 34 shown in FIG. 9 also contains polymer 36 in the form of aporous matrix about fibers 33.

It is clear from FIGS. 6-9 that fabrics and wound dressings of thepresent invention contain a porous polymeric matrix dispersed on thesurfaces and substantially homogeneously through the fabric. Due to theporous nature of the matrix, body fluids are permitted to pass into thematrix, where ample surface area of polymer is present to interact withthe body fluids. This results in faster and a higher degree ofhemostasis, particularly where bleeding is occurring at a high volumeand rate.

It also is clear from FIGS. 3-5 that comparative fabrics and wounddressings do not contain a porous, polymeric matrix, either on a surfaceof the dressing or dispersed throughout the fabric. As a result, theamount of polymer present to interact with body fluids is significantlyreduced. In addition, due to the formation of agglomerated polymerlayers during air drying, body fluids are not permitted to pass freelyinto the wound dressing where they can interact with and bind to thedressing. Both of these characteristics result in less hemostasis, suchthat wound dressings of this construct do not provide and maintainhemostasis in cases of severe bleeding. Additionally, such fabrics werefound to be brittle and stiff, such that placement within andconformance to a wound site by a physician is not acceptable.

As shown in FIGS. 6 and 7, the polymer matrix disposed on the respectivesurfaces contains countless pores, ranging from about ten microns to aslarge as about 400 microns in diameter, or greater. FIG. 6 shows surface32 of fabric 30. As noted, polymer 36 is present in the form of a porousmatrix about fibers 33, thereby providing ample polymer surface areawith which body fluids can interact upon contact therewith. Surface 34shown in FIG. 7 also contains polymer 36 in the form of a porous matrixdispersed about fibers 33, thereby generating a sponge-like polymermatrix structure in concert with the fibers.

It is clear from FIGS. 6-7 that fabrics and wound dressings of thepresent invention contain a porous polymeric matrix dispersed on thesurface and substantially homogeneously through the fabric. Due to theporous nature of the matrix, body fluids are permitted to pass into thematrix, where ample surface area of polymer is present to interact withthe body fluids. This results in faster and a higher degree ofhemostasis.

Hemostatic wound dressings fabricated from aldehyde-oxidized regeneratedcellulose according to the present invention are represented in FIGS.10-12.

As shown in FIG. 10, a porous, polymer matrix is substantially uniformlydistributed on surface 42 and throughout fabric 40. Polymer 46 forms aporous, polymer matrix integrated with the knitted fibers 43. Theporous, polymer matrix exhibits significant liquid absorption propertiesfrom capillary action in the same manner as a sponge.

As shown in FIGS. 11 and 12, the polymer matrix disposed on the relativesurfaces contains countless pores, ranging from about ten microns to aslarge as about 400 microns in diameter, or greater. FIG. 11 showssurface 42 of fabric 40. As noted, polymer 46 is present in the form ofa porous matrix about fibers 43, thereby providing ample polymer surfacearea with which body fluids can interact upon contact therewith.Opposing surface 44 shown in FIG. 12 also contains polymer 46 in theform of a porous matrix dispersed about fibers 43, thereby generating asponge-like polymer matrix structure in concert with the fibers.

It is clear from FIGS. 10-12 that fabrics and wound dressings of thepresent invention contain a porous, polymeric matrix dispersed on thesurfaces and substantially homogeneously through the fabric. Due to theporous nature of the matrix, body fluids are permitted to pass into thematrix, where ample surface area of polymer is present to interact withthe body fluids. This results in faster and a higher degree ofhemostasis.

As stated above, in order to preserve the porous structure of thepolymeric matrix and the homogeneity thereof, it is important tomaintain the preferred weight ratio of polymer to fabric during theprocess of making the wound dressing and the homogenous distribution ofthe polymer solution on the surface of and throughout the fabricsubstrate in order to avoid defects on and throughout the wounddressing. In a laboratory setting, this is readily achieved, as thecontacting of the fabric substrate with the polymer solution in thelaboratory crystallization dish, saturation of the fabric substratematerial in the polymer solution and the subsequent lyophilization ofthe fabric and solution in the dish all take place in the lyophilizationunit, where a precise quantity of water-soluble and water-swellablepolymer can be used to prepare the solution. No transfer of thesaturated fabric or the dish into the lyophilization unit is necessary.As a result, a homogeneous distribution of polymer on fabric isachieved. However, in a manufacturing setting, due to its larger scale,such a process is no longer feasible. A larger container, e.g. a tray orpan, is used instead to hold the fabric and the polymer solution duringcontacting and saturation of the fabric by the solution, which isconducted outside of the lyophilization unit. The saturated fabric thenmust be transferred into the lyophilization unit for further processing.

Certain problems are associated with producing a wound dressing of thepresent invention on a larger scale as described above, where the wounddressing will possess mechanical and hemostatic properties suitable foruse as a hemostatic dressing. For instance, if one were to attempt totransfer the container having the polymer solution and saturated fabricdisposed therein into the lyophilization unit, during transfer of thecontainer into the lyophilization unit, it is difficult to maintain aconstant level of the polymer solution above the fabric in the tray dueto movement, e.g. shifting or “sloshing”, of the solution in relation tothe fabric. In some cases during movement of the container, the fabricsurface may even be exposed and the turbulence of the shifting polymersolution in the container may result in poor distribution of polymer onthe surface of and through the fabric, particularly with respect to thedistribution of the polymer on the surface. This in turn is detrimentalto the effectiveness of the hemostatic property of the wound dressing.

In order to maintain the level of solution above the fabric surfaceprior to lyophilization to ensure that the fabric remains immersed inthe polymer solution in order to provide homogeneous distribution on andthroughout the fabric, an excess amount of polymer solution must beplaced in the container. However, such an approach has not beensuccessful because such an excess amount of polymer solution may resultin an undesirable weight ratio of polymer to fabric, which consequentlyleads to a loss in the flexibility of the wound dressing and of themicroporous structure of the polymeric matrix of the hemostatic wounddressing.

To solve this problem, processes of the present invention utilize atransfer support means, e.g. a transfer sheet or carrier, in order totransfer the saturated fabric from the container used to saturate thefabric with polymer solution into the lyophilization unit. However, inorder to maintain the homogeneous distribution of the porous, polymericmatrix on and through the fabric substrate after lyophilization, cautionmust be exercised to minimize disturbance of the homogenous distributionof polymer solution in relationship to the fabric and to minimizedeformation, e.g. stretching or tearing, of the fabric substrate duringtransfer into the lyophilization unit. In addition, the formation of airbubbles or voids between the fabric substrate and the transfer supportmeans while transferring the fabric to the support means must besubstantially avoided so as not to create an unacceptable number defectsin the wound dressing.

In accordance with the invention, the method provides for the transferof the saturated fabric substrate onto the transfer support mean andtransferring the saturated fabric substrate and support means to alyophilization unit. As shown in FIGS. 13-15, where like numbers areused to identify like features, polymer solution 62 is placed incontainer 60. Fabric 64 then is placed in container 60 and submerged insolution 62 for a period of time sufficient to saturate fabric 64 withsolution 62. Saturated fabric substrate 64 is transferred from container60 onto support means 66 in a manner such that the homogenousdistribution of polymer solution on and through the fabric issubstantially maintained and that the presence of defects due to airthat has been trapped between the fabric and support means is minimized.

The transfer of saturated fabric 64 onto support means 66 isaccomplished in a fashion to create a hydraulic pressure sufficient toallow air bubbles to escape from between the fabric substrate and thesupport means. Distal end 64 b of fabric 64 is joined with support means66 and moved in a continuous fashion as shown, at a controlled rate,while maintaining a desired angle of incidence 68 between fabric 64 andsupport means 66 until proximal end 64 a also is supported by supportmeans 66 to prevent, or at least minimize bubble formation. At the sametime, maintaining such conditions of transfer also prevent, or at leastminimize, physical deformation of the substrate, such as stretching ortearing. Preferably, the angle of incidence between the fabric and thesupport means will range from about 20° to about 90°. More preferably,the angle of incidence will range from about 30° to about 60°. Even morepreferably, the angle of incidence will be about 45°. The rate ofadvancing the fabric onto the support means preferably will range fromabout 8 inches per minute to about 2 inches per minute. Preferably, therate of transfer is about 7 inches per minute.

The support means should be made of an inert material that will notrelease any toxic chemical substance or any substance that may alter thecharacteristics of the wound dressing. It is important that the supportmeans does not alter the freezing and drying parameters associated withthe lyophilization process stated above. Therefore, the material usedfor the support means should be cryolitically stable, such that it maywithstand extremely low temperatures without deformation, preferablydown to about −50° C. If the support means is not stable at lowtemperatures, deformation of the means will lead to defects in the wounddressing.

It is important that the support means used for transferring thesaturated fabric is of density, mechanical strength, flexibility andthickness to provide sufficient support for the fabric, while avoidingexcessive bending and mechanical deformation of the saturated fabricsubstrate. If the support means is too thick and rigid, it may bedifficult to slide the saturated fabric onto the support means. If thesupporting means is too soft and flexible, the saturated fabric may bendexcessively, thereby causing stretching or other mechanical deformation,which may lead to pooling and running of the polymer solution on thesurface, or the creation of surface defects during lyophilization.

It is also important that the support means used for transferring thefabric substrate provides a smooth and flat surface to prevent airbubbles from being trapped under the saturated fabric substrate. Thetransfer means further must possess heat transfer efficiency suitablefor rapid freezing of the fabric/polymer construct and removal of thesolvent under high vacuum in the lyophilization unit so as to maintainthe homogenous distribution of the porous, polymer matrix on and throughthe fabric substrate after lyophilization. By heat transfer efficiency,it is meant that heat is transferred quickly from the support means tothe saturated fabric to facilitate rapid freezing. A preferred supportmeans is a high-density polyethylene sheet having a preferred thicknessof between about 50 mils and about 200 mils. Most preferred supportmeans is high-density polyethylene having a preferred thickness ofbetween about 60 mils and about 100 mils.

Wound dressings that have been prepared according to the inventiveprocess set forth in example 27 are depicted in FIGS. 16 a-16 c. Asshown therein, the distribution of lyophilized polymer on both surface52 and surface 54 of wound dressing 50 is substantially homogenous.Furthermore, surface 54, contacting the support means, is free ofdefects caused by entrapped air bubbles.

Wound dressings prepared by comparative processes according to examples28 and 29 are depicted in FIGS. 17 a-17 c and 18 a-18 c. As shown FIGS.17 a-17 c, the distribution of lyophilized polymer is not homogenous andexcess polymer 72, present as a result of improper transfer of thefabric to the support means, is present throughout both surfaces 78 and79. Fabric 76 is shown between excess polymer build-up 72. In addition,defects 74 are present, resulting from air bubbles trapped between thesupport means and surface 79.

Similar results are depicted in FIGS. 18 a-18 c, where fabric 80includes excess polymer build-up 82 both on surface 88 and surface 89.Surface 89, having contacted the support means, also includes defects 84and 85. Defects 85 are due to the support means being too thin andunstable during lyophilization. Fabric 86 is shown between excesspolymer build-up 82.

Similar results also are depicted in FIGS. 19 a-19 c, where fabric 90includes excess polymer build-up 92 both on surface 98 and surface 99.Surface 99, having contacted the support means, also includes defects94. Fabric 96 is shown between excess polymer build-up 92.

Once the fabric substrate has the polymeric matrix formed, individualwound dressing patches may be formed from the substrate into any desiredshaped. As shown in FIG. 20, several individual patches 92 may beformed, for instance, into an octagonal shape from the fabric substrate.Wound dressing 100 is shown in FIG. 21. Any shape that is suitable foruse as a wound dressing may be utilized, as one skilled in the art willreadily ascertain from the description. The individual dressing may beformed by, for instance, die cutting, laser cutting, or any method thatdoes not detrimentally affect the hemostatic properties of the dressing.

While the following examples demonstrate certain embodiments of theinvention, they are not to be interpreted as limiting the scope of theinvention, but rather as contributing to a complete description of theinvention.

EXAMPLE 1 Carboxylic-Oxidized Regenerated Cellulose (CORC)/HEC PorousPatch Preparation

One gram of hydroxyethyl cellulose (HEC, from Aldrich) was dissolved in99 grams of deionized water. After complete dissolution of the polymer,10 grams of the HEC solution was transferred into a crystallization dishwith a diameter of 10 cm. A piece of Surgicel Nu-Knit® absorbablehemostat, based on CORC, having a diameter of 9.8 cm (about 1.3 gram)was placed on the HEC solution in the crystallization dish. Aftersoaking the fabric in the solution for 3 minutes, the wet fabric in thedish was then lyophilized overnight. A very flexible patch was formed.The patch was further dried at room temperature under vacuum.

EXAMPLE 2 CORC/CS Porous Patch Preparation

One gram of cellulose sulfate (CS, from ACROS Organics) was dissolved in99 grams of deionized water. After complete dissolution of the polymer,10 grams of the CS solution was transferred into a crystallization dishwith a diameter of 10 cm. A piece of Surgicel Nu-Knit® absorbablehemostat with a diameter of 9.8 cm (about 1.3 gram) was placed on the CSsolution in the crystallization dish. After soaking the fabric for 3minutes, the wet fabric was then lyophilized overnight. A very flexiblepatch was formed. The patch was further dried at room temperature undervacuum.

EXAMPLE 3 CORC/MC Porous Patch Preparation

One gram of methyl cellulose (MC, from Aldrich) was dissolved in 99grams of deionized water. After complete dissolution of the polymer, 10grams of the MC solution was transferred into a crystallization dishwith a diameter of 10 cm. A piece of Surgicel Nu-Knit® absorbablehemostat with a diameter of 9.8 cm (about 1.3 gram) was placed on the MCsolution in the crystallization dish. After soaking the fabric for 3minutes, the wet fabric in the dish was then lyophilized overnight. Avery flexible patch was formed. The patch was further dried at roomtemperature under vacuum.

EXAMPLE 4 CORC/Water-Soluble Chitosan (WS—CH) Porous Patch Preparation

One gram of WS—CH was dissolved in 99 grams of deionized water. Aftercomplete dissolution of the polymer, 10 grams of the WS—CH solution wastransferred into a crystallization dish with a diameter of 10 cm. Apiece of Surgicel Nu-Knit® absorbable hemostat with a diameter of 9.8 cm(about 1.3 gram) was placed on WS—CH solution in the crystallizationdish. After soaking the fabric for 3 minutes, the wet fabric in the dishwas then lyophilized overnight. A very flexible patch was formed. Thepatch was further dried at room temperature under vacuum.

EXAMPLE 5 CORC/Na—CMC Porous Patch Preparation

One gram of sodium salt of CMC (Na—CMC, from Aqualon) was dissolved in99 grams of deionized water. After complete dissolution of the polymer,10 grams of the Na—CMC solution was transferred into a crystallizationdish with a diameter of 10 cm. A piece of Surgicel Nu-Knit® absorbablehemostat with a diameter of 9.8 cm (about 1.3 gram) was placed on theCMC solution in the crystallization dish. After soaking the fabric for 3minutes, the wet fabric in the dish was then lyophilized overnight. Avery flexible patch was formed. The patch was further dried at roomtemperature under vacuum.

COMPARATIVE EXAMPLE 6 CORC/Na—CMC Film Preparation

One gram of sodium salt of CMC (Na—CMC, from Aqualon) was dissolved in99 grams of deionized water. After complete dissolution of the polymer,10 grams of the Na—CMC solution was transferred into a crystallizationdish with a diameter of 10 cm. A piece of Surgicel Nu-Knit® absorbablehemostat with a diameter of 9.8 cm (about 1.3 gram) was placed on theNa—CMC solution in the crystallization dish. The wet fabric in the dishwas then air-dried overnight. A rigid and brittle patch was formed. TheCORC/Na—CMC film was further dried at room temperature under vacuum. Thefilm was not effective as a hemostat because it was too stiff and didnot conform to the bleeding site well.

EXAMPLE 7 Na—CMC Porous Patch Preparation

One gram of sodium salt of CMC (Na—CMC, medium viscosity grade fromSigma) was dissolved in 99 grams of deionized water. After completedissolution of the polymer, 60 grams of the Na—CMC solution wastransferred into a crystallization dish with a diameter of 10 cm. Thesolution in the dish was then lyophilized overnight. A porous sponge wasformed. The patch was further dried at room temperature under vacuum.

EXAMPLE 8 Hemostatic Performance of Different Materials in PorcineSplenic Incision Model

A porcine spleen incision model was used for hemostasis evaluation ofdifferent materials. The materials were cut into 2.5 cm×1.5 cmrectangles. A linear incision of 1.5 cm with a depth of 0.3 cm was madewith a surgical blade on a porcine spleen. After application of the testarticle, digital tamponade was applied to the incision for 2 minutes.The hemostasis was then evaluated. Additional applications of digitaltamponade for 30 seconds each time were used until complete hemostasiswas achieved. Fabrics failing to provide hemostasis within 12 minuteswere considered to be failures. Table 1 lists the results of theevaluation.

TABLE 1 Hemostatic performance of different materials Percent of testsamples to achieve hemostasis within the time period 0-2 2-3 3-4 4-5 5-6<12 Material (min) (min) (min) (min) (min) (min) Surgicel Nu-Knit ®  0%0% 100% Example 1 patch 100% Example 2 patch 100% Example 3 patch 100%Example 4 patch 100% Example 5 patch 100% Example 6 film  50% 50%Example 7 sponge 0 Surgical gauze 0

As indicated from the results, wound dressings prepared usinglyophilization as the means for removing solvent improved hemostaticproperty of hemostatic fabrics, while the air-dried process failed toenhance the hemostatic property of hemostatic fabrics. Additionally,lyophilized Na—CMC sponge alone failed to achieve hemostasis.

EXAMPLE 9 Hemostatic Performance of Example 5 (CORC/Na—CMC) in a PorcineSplenic Arterial Needle Puncture Model

A puncture defect was made on a porcine splenic artery with an 18-gaugeneedle. After the needle was removed, severe bleeding was observed. Atest article (2.5 cm×2.5 cm) was applied over the puncture site. Digitalpressure was applied over the test article for 2 minutes. The hemostaticperformance was evaluated. The observations are listed in Table 2.

TABLE 2 Comparison of Initial time to Hemostasis and Ability ofMaintaining Hemostasis # of Digital Initial Time to Maintenance ofMaterial Pressure Hemostasis Hemostasis Surgicel Nu-Knit ® 1 <2 minRe-bleeding occurred after 4 min Example 5 Patch 1 <2 min No Re-bleedingoccurred

EXAMPLE 10 Hemostatic Performance of Different Materials in a PorcineSplenic Incision Model with Tamponade for 30 Seconds

A porcine spleen incision model was used for hemostasis evaluation ofdifferent materials. The materials were cut into 2.5 cm×1.5 cmrectangles. A linear incision of 1.5 cm with a depth of 0.3 cm was madewith a surgical blade on porcine spleen. After application of the testarticle, digital tamponade was applied to the incision for 30 seconds.The hemostasis evaluation was then performed. Additional applications ofdigital tamponade for 30 seconds each time were used until completehemostasis was achieved. Table 3 lists the results of the evaluation.

TABLE 3 Hemostatic performance of different materials in a splenicincision model Material # of Digital Pressure Time to HemostasisSurgicel Nu-Knit ® 5 2 min 55 sec Example 5 Patch 1 <30 sec

EXAMPLE 11 Hemostatic Performance of Different Materials in a PorcineSplenic Cross-Hatch Model

A porcine spleen cross-hatch model was used for hemostasis evaluation ofdifferent materials. The materials were cut into 3 cm×3 cm squares. Asurgical defect (2 cm×2 cm, 0.2 cm deep) was made with a surgical bladeon the porcine spleen. Additional bleeding was induced by making threeadditional equally spaced, side-to-side horizontal incisions and threeadditional equally spaced, side-to-side vertical incisions within thedefect. After application of the test article, digital tamponade wasapplied to the incision for 2 minutes. The hemostasis evaluation wasthen performed. Additional applications of digital pressure for 30second each time were used until complete hemostasis was achieved. Table4 lists the results of the evaluation.

TABLE 4 Hemostatic performance of different materials in a spleniccross-hatch model Material # of Digital Pressure Time to HemostasisSurgicel Nu-Knit ® 4 3 min 55 sec Example 5 Patch 1 <2 min

EXAMPLE 12 Preparation of Knitted Aldehyde-Oxidized Regenerated (AORC)Cellulose Fabric

A 15.8 g piece of knitted rayon fabric as described herein was cut inthe form of a strip 1.5 inches wide. The strip was wound on a mandreland suspended in 600 ml of aqueous isopropyl alcohol (IPA) (200 mlIPA/400 ml de-ionized (DI) water). 20.8 g of sodium periodate (Aldrich,Milwaukee, 53201) was dissolved in the solution (1:1 molar ratio) andthe mandrel was rotated at moderate rpm in the solution for 21 hours atambient temperature. It is essential that the oxidation of the fabric beconducted in the dark. The solution pH was 3.8. The solution wasdiscarded after the reaction. The mandrel with the oxidized fabric waswashed for 30 minutes in 1 liter of cold DI water containing 50 ml ofethylene glycol. It was then washed with aqueous IPA (50/50) for 15minutes, followed by a pure IPA wash for 15 minutes. The fabric wasdried in ambient air for several hours.

The oxidized fabric then was evaluated for hemostasis as set forthbelow. Results are provided in Table 5.

EXAMPLE 13 Preparation of Water-Soluble Aldehyde-OxidizedMethylcellulose (AOMC)

100 g of a 5% methylcellulose (MC, Ave. Mn 63 kD, lot# 06827ES fromAldrich, Milwaukee, Wis.) aqueous solution was combined with 3 g ofperiodic acid (Aldrich, Milwaukee, 53201) and was then stirred for 5hours at ambient temperature in the dark. 1.5 ml of ethylene glycol wasadded to the reaction solution and stirred for 30 minutes. 2000 ml ofacetone were added slowly into the reaction solution to precipitate theAOMC. The reaction mixture was allowed to stand for 20-30 minutes toseparate the liquid phase from the solid phase. The supernatant then wasremoved and the solid phase centrifuged to precipitate the solids. Thesolid precipitate was dissolved in 100 ml DI over night followed bydialysis for 72 hours. The final wet mixture was lyophilized to form asponge/foam.

EXAMPLE 14 Preparation of Water-Soluble Aldehyde-Oxidized HydroxyethylCellulose (AOHC)

100 g of a 5% hydroxyethyl cellulose (HEC, Ave. Mv; 720 kD lot # 02808DUfrom Aldrich, Milwaukee, Wis.) aqueous solution was combined with 3 g ofperiodic acid (Aldrich, Milwaukee, 53201) and was then stirred for 5hours at ambient temperature in the dark. 1.5 ml of ethylene glycol wasadded to the reaction solution and stirred for 30 minutes. 2000 ml ofacetone were added slowly into the reaction solution to precipitate theAOHC. The reaction mixture was allowed to stand for 20-30 minutes toseparate the liquid phase from the solid phase. The supernatant then wasremoved and the solid phase centrifuged to precipitate the solids. Thesolid precipitate was dissolved in 100 ml DI over night followed bydialysis for 72 hours. The final wet mixture was lyophilized to form asponge/foam.

EXAMPLE 15 AORC/HEC Porous Patch Preparation

One gram of hydroxyethyl cellulose (HEC, Lot # GI01 from TCI, Tokyo,Japan) was dissolved in 99 grams of deionized water. After completedissolution of the polymer, 10 grams of the HEC solution was transferredinto a crystallization dish with a diameter of 10 cm. A piece of AORCfabric (about 1.3 gram) was placed on the HEC solution in thecrystallization dish. After soaking the fabric in the solution for 3minutes, the wet fabric in the dish was lyophilized overnight. A veryflexible patch was formed. The patch was further dried at roomtemperature under vacuum. The AORC/HEC patch then was evaluated forhemostasis as set forth below. Results are provided in Table 5.

EXAMPLE 16 AORC/CS Porous Patch Preparation

One gram of cellulose sulfate (CS, lot # A013801301 from ACROS Organics,New Jersey) was dissolved in 99 grams of deionized water. After completedissolution of the polymer, 10 grams of the CS solution was transferredinto a crystallization dish with a diameter of 10 cm. A piece of AORCfabric (about 1.3 gram) was placed on the CS solution in thecrystallization dish. After soaking the fabric for 3 minutes, the wetfabric was lyophilized overnight. A very flexible patch was formed. Thepatch was further dried at room temperature under vacuum.

The AORC/CS patch then was evaluated for hemostasis as set forth below.Results are provided in Table 5.

EXAMPLE 17 AORC/MC Porous Patch Preparation

One gram of methyl cellulose (MC, Ave. Mn 63 kD, lot# 06827ES fromAldrich, Milwaukee, Wis.) was dissolved in 99 grams of deionized water.After complete dissolution of the polymer, 10 grams of the MC solutionwas transferred into a crystallization dish with a diameter of 10 cm. Apiece of AORC fabric (about 1.3 gram) was-placed on the MC solution inthe crystallization dish. After soaking the fabric for 3 minutes, thewet fabric in the dish was lyophilized overnight. A very flexible patchwas formed. The patch was further dried at room temperature undervacuum.

The AORC/MC patch then was evaluated for hemostasis as set forth below.Results are provided in Table 5.

EXAMPLE 18 AORC/CMC—Na Porous Patch Preparation

One gram of sodium salt of carboxymethyl cellulose (CMC—Na, Type 7M8SFLot#: 77521 from Aqualon, Wlmington, Del.) was dissolved in 99 grams ofdeionized water. After complete dissolution of the polymer, 10 grams ofthe Na—CMC solution was transferred into a crystallization dish with adiameter of 10 cm. A piece of AORC fabric (about 1.3 gram) was placed onthe CMC solution in the crystallization dish. After soaking the fabricfor 3 minutes, the wet fabric in the dish was lyophilized overnight. Avery flexible patch was formed. The patch was further dried at roomtemperature under vacuum.

The AORC/CMC—Na patch then was evaluated for hemostasis as set forthbelow. Results are provided in Table 5.

EXAMPLE 19 AORC/CMC—Na Porous Patch Preparation

One gram of sodium salt of carboxymethyl cellulose (CMC—Na, Type: 7H4FLot#: 79673 from Aqualon, Wilmington, Del.) was dissolved in 99 grams ofdeionized water. After complete dissolution of the polymer, 10 grams ofthe Na—CMC solution was transferred into a crystallization dish with adiameter of 10 cm. A piece of AORC fabric (about 1.3 gram) was placed onthe CMC solution in the crystallization dish. After soaking the fabricfor 3 minutes, the wet fabric in the dish was then lyophilizedovernight. A very flexible patch was formed. The patch was further driedat room temperature under vacuum.

The AORC/CMC—Na patch then was evaluated for hemostasis as set forthbelow. Results are provided in Table 5.

EXAMPLE 20 AORC/HEC Porous Patch Preparation

One gram of hydroxyethyl cellulose (HEC, Ave. Mv; 720 kD lot # 02808DUfrom Aldrich, Milwaukee, Wis.) was dissolved in 99 grams of deionizedwater. After complete dissolution of the polymer, 10 grams of the HECsolution was transferred into a crystallization dish with a diameter of10 cm. A piece of AORC fabric (about 1.3 gram) was placed on the HECsolution in the crystallization dish. After soaking the fabric in thesolution for 3 minutes, the wet fabric in the dish was lyophilizedovernight. A very flexible patch was formed. The patch was further driedat room temperature under vacuum.

The AORC/HEC patch then was evaluated for hemostasis as set forth below.Results are provided in Table 5.

EXAMPLE 21 AORC/HEC/Thrombin Porous Patch Preparation

One gram of hydroxyethyl cellulose (HEC, Ave. Mv; 720 kD lot # 02808DUfrom Aldrich, Milwaukee, Wis.) was dissolved in 99 grams of deionizedwater. After complete dissolution of the polymer, 20 ml of the MCsolution was used to reconstitute thrombin in a vial (20,000 units). 2.5ml of the cloudy solution was transferred into a crystallization dish. Apiece of AORC fabric (about 1 gram) was placed on the HEC solution inthe crystallization dish. After soaking the fabric in the solution for 3minutes, the wet fabric in the dish was lyophilized overnight. A veryflexible patch was formed. The patch was further dried at roomtemperature under vacuum.

The AORC/HEC/Thrombin porous patch then was evaluated for hemostasis asset forth below. Results are provided in Table 5.

EXAMPLE 22 AORC/MC/Thrombin Porous Patch Preparation

One gram of methyl cellulose (MC, Ave. Mn 63 kD, lot# 06827ES fromAldrich) was dissolved in 99 grams of deionized water. After completedissolution of the polymer, 20 ml of the MC solution was used toreconstitute thrombin in a vial (20,000 units). 2.5 ml of the cloudysolution was transferred into a crystallization dish. A piece of AORCfabric (about 1 gram) was placed on the MC solution in thecrystallization dish. After soaking the fabric in the solution for 3minutes, the wet fabric in the dish was lyophilized overnight. A veryflexible patch was formed. The patch was further dried at roomtemperature under vacuum.

The AORC/MC/Thrombin porous patch then was evaluated for hemostasis asset forth below. Results are provided in Table 5.

EXAMPLE 23 AORC/AOMC/Thrombin Porous Patch Preparation

One gram of AOMC from Example 13 was dissolved in 99 grams of deionizedwater. After complete dissolution of the polymer, 20 ml of the AOMCsolution was used to reconstitute thrombin in a vial (20,000 units). 2.5ml of the cloudy solution was transferred into a crystallization dish. Apiece of AORC fabric (about 1 gram) was placed on the AOMC solution inthe crystallization dish. After soaking the fabric in the solution for 3minutes, the wet fabric in the dish was lyophilized overnight. A veryflexible patch was formed. The patch was further dried at roomtemperature under vacuum.

EXAMPLE 24 AORC/AOHEC/Thrombin Porous Patch Preparation

One gram of AOHEC(MW=90 kD, from Aldrich) synthesized as per example 3was dissolved in 99 grams of deionized water. After complete dissolutionof the polymer, 20 ml of the AOHEC solution was used to reconstitutethrombin in a vial (20,000 units). 2.5 ml of the cloudy solution wastransferred into a crystallization dish. A piece of AORC fabric (about 1gram) was placed on the AOHEC solution in the crystallization dish.After soaking the fabric in the solution for 3 minutes, the wet fabricin the dish was lyophilized overnight. A very flexible patch was formed.

The patch was further dried at room temperature under vacuum.

The AORC/AOHEC/Thrombin porous patch then was evaluated for hemostasisas set forth below. Results are provided in Table 5.

EXAMPLE 25 Hemostatic Performance of Different Materials in PorcineSplenic Incision Model

A porcine spleen incision model was used for hemostasis evaluation ofdifferent materials. The materials were cut into 2.5 cm×1.5 cmrectangles. A linear incision of 1.5 cm with a depth of 0.3 cm was madewith a surgical blade on a porcine spleen. After application of the testarticle, digital tamponade was applied to the incision for 2 minutes.The hemostasis was then evaluated. Additional applications of digitaltamponade for 30 seconds each time were used until complete hemostasiswas achieved. Fabrics failing to provide hemostasis within 12 minuteswere considered to be failures. Table 5 lists the results of theevaluation.

EXAMPLE 26 Hemostatic Performance of Different Materials in a PorcineSplenic Incision Model With Tamponade for 30 Seconds

A porcine spleen incision model was used for hemostasis evaluation ofdifferent materials. The materials were cut into 2.5 cm×1.5 cmrectangles. A linear incision of 1.5 cm with a depth of 0.3 cm was madewith a surgical blade on porcine spleen. After application of the testarticle, digital tamponade was applied to the incision for 30 seconds.The hemostasis evaluation was then performed. Additional applications ofdigital tamponade for 30 seconds each time were used until completehemostasis was achieved. Table 5 lists the results of the evaluation.

TABLE 5 Hemostatic performance of AORC-Based Materials 2 min tamponade30 second tamponade Time to Hemostasis Time to Hemostasis Sample(Seconds) (Seconds) Example 12  187 (n = 11) Example 15 370 (n = 2)Example 16 308 (n = 2) Example 17 285 (n = 1) Example 18 582 (n = 2)Example 19 120 (n = 3) 230 (n = 2) Example 20 187 (n = 3) 253 (n = 2)Example 21  73 (n = 3) Example 22  30 (n = 3) Example 24  47 (n = 3)Surgical gauze Negative >720 >720 Control

As indicated from the results, wound dressings of the present inventionachieve effective hemostasis. In particular, when higher molecularweight water-soluble polymers (CMC—Na and HEC) were used, thecorresponding patches achieved better time to hemostasis. Also asindicated from the results, wound dressings of the present inventionhaving hemostatic agents, e.g. thrombin, bound there to achieve evenfaster time to hemostasis.

EXAMPLE 27 Preparation of CORC/Na—CMC Wound Dressing According toPresent Invention

410 grams of sodium salt of CMC (Na—CMC, from Aqualon) was dissolved in41 liters of sterile water and transferred to a holding tray. A piece ofknitted CORC fabric as described herein was cut to 7 in×7 in (about 6grams) and carefully placed in the Na—CMC solution in the tray, takingcare to avoid the entrapment of any air bubbles (Na—CMC solution:knittedCORC fabric ratio is 15:1). The fabric was soaked in the polymersolution for 1-3 minutes. One end of the saturated fabric then wascarefully lifted with minimal stretching and placed on a flexiblehigh-density polyethylene support sheet (10 in×14 in×0.0133 in) to jointhe edges of saturated fabric and support sheet. The adjoined edges wereheld together and both the support sheet and fabric were forwardedtogether in a continuous fashion at a constant rate, while maintainingan angle of incidence between the sheet and fabric of about 45 degreesor less to generate a sufficient hydrolic pressure from the saturatedfabric to the support sheet to remove any air bubbles that may havebecome trapped between the saturated fabric and the support sheet. Afterthe saturated fabric was fully transferred onto the support sheet, thesupport sheet having the saturated fabric disposed thereon was placed onthe shelf of a Usifroid (Model No—SMH1575, Serial No—16035)lyphilization unit at a temperature of approximately −50° C. The frozen,saturated fabric on the support sheet then underwent a fulllyophilization cycle. A flexible patch with a substantial homogenousdistribution of Na—CMC through on and through the fabric was formed. Thepatch was further dried at 50° C. for 4 hours before packaging.

EXAMPLE 28 Preparation of ORC/Na—CMC Comparative Wound Dressing

410 gram of sodium salt of CMC (Na—CMC, from Aqualon) was dissolved in41 liters of sterile water and then transferred to a tray. A piece ofknitted CORC fabric as described herein was cut into 7 in×7 in (about 6gram) and carefully placed on the Na—CMC solution in the tray withouttrapping any air bubbles (Na—CMC solution:knitted CORC fabric ratio is15:1). The fabric was soaked for 1-3 minutes in order to saturate thefabric with the polymer solution. Immediately upon saturation of thefabric, the saturated fabric was lifted from the container and solutionand laid manually onto a flexible high-density polyethylene supportsheet of the same type used in Example 27 (10 in×14 in×0.0133). Thesupport sheet having the saturated fabric place thereon then was placedon the shelf of a Usifroid (Model No—SMH1575, Serial No—16035)lyophilization unit at a temperature of approximately −50° C. Thefrozen, saturated fabric on the support sheet then underwent a fulllyophilization cycle. A flexible patch having defects caused by trappedair bubbles and an uneven distribution of Na—CMC on the fabric wasformed.

EXAMPLE 29 Preparation of CORC/Na—CMC Comparative Wound Dressing

410 gram of sodium salt of CMC (Na—CMC, from Aqualon) was dissolved in41 liters of sterile water and then transferred to in tray. A piece ofknitted CORC fabric as described herein was cut into 7 in×7 in (about 6gram) and carefully laid down on the Na—CMC solution in the tray withouttrapping any air bubbles (Na—CMC solution:knitted CORC fabric ratio is15:1). The fabric was soaked for 1-3 minutes to allow saturation of thefabric by the polymer solution. Immediately upon saturation of thefabric, the saturated fabric was lifted from the solution and containerand transferred manually by hands onto a flexible high-densitypolyethylene thin film. The saturated fabric on the HDPE thin film wasthen placed on the shelf of a Usifroid (Model No—SMH1575, SerialNo—16035) lyophilization unit at a temperature of approximately —50° C.The frozen, saturated fabric on the thin film (thickness less than 0.005in) then underwent a full lyophilization cycle. A very flexible patchwith trapped air bubbles and uneven distribution of Na—CMC throughknitted CORC fabric was formed. In addition, defects were noted in theform of “lines”, due to the instability of the thin film duringlyophilization.

EXAMPLE 30 Hemostatic Performance of Wound Dressings in Porcine SplenicIncision Model

A porcine spleen incision model was used for hemostasis evaluation ofwound dressings prepared according to Examples 27-29, using a standardhemostatic wound dressing as a standard. The materials were cut into 2.5cm×1.5 cm rectangles. A linear incision of 1.5 cm with a depth of 0.3 cmwas made with a surgical blade on a porcine spleen. After application ofthe test article, digital tamponade was applied to the incision for 2minutes. The hemostasis was then evaluated. Additional applications ofdigital tamponade for 30 seconds each time were used until completehemostasis was achieved. Approximately 100% of tested articles toachieve hemostasis within 3 minutes are considered to demonstrate goodhemostatic efficacy. Table 6 lists the results of the evaluation.

TABLE 6 Hemostatic performance of dressings Percent of test samples toachieve hemostasis within the time period 0–3 4–7 Sample (min) (min)Surgicel Nu-Knit ®  0% 100% Example 27 100% 100% Example 28  0% 100%Example 29  0% 100%

As indicated from Table 6, hemostatic wound dressings prepared by theprocess of the present invention provide hemostasis faster, while thoseprepared by comparative processes fail to provide similarly rapidhemostasis.

EXAMPLE 31 Method of Analysis for Water-Soluble Oligosaccharides

150.0 mg of the conditioned fabric substrate to be analyzed is cut to asize approximately 0.5″×2″ and placed into a test tube. The test tube isfilled with approximately 30 ml of with distilled or deionized water anda stopper placed in the test tube. The tube then is stored at 70° C. forapproximately 17-18 hours. The substrate sample is filtered through aglass crucible having a fritted disc of coarse or medium porosity. Thefiltrate containing the water-soluble oligosaccharide is transferred topre-weighed aluminum dishes and evaporated to dryness. The residue iscooled in a desiccator containing phosphorous pentoxide and weighed. Thewater-soluble oligosaccharide content is calculated using the formula:% Water-soluble oligosaccharide Content=[(Bf)/Wt]×100where Bf is the weight of the water-soluble oligosaccharide (filtrate)and Wt is the total weight of the residue and filtrate.

1. A process for making a wound dressing for use with moderate to severebleeding, the wound dressing comprising a fabric substrate thatcomprises oxidized regenerated cellulose fibers and from about 8 toabout to about 20 percent by weight of water-soluble oligosaccharides;and a biocompatible, water-soluble or water-swellable polymer matrix ofsodium carboxymethyl cellulose, the process consisting of the steps of:providing a solution having dissolved therein sodium carboxymethylcellulose, providing a fabric substrate having a first surface and asecond surface opposing said first surface, said fabric substrate havingflexibility, strength and porosity effective for use as a hemostat, saidfabric substrate comprising a carboxylic-oxidized cellulose fibers andfrom about 8 to about 20 percent by weight of water-solubleoligosaccharides, contacting said solution with said fabric substrateunder conditions effective to substantially homogeneously distributesaid solution on said first and second surfaces and through said fabricsubstrate, lyophilizing said fabric substrate with said solutiondistributed there through, thereby forming a porous, polymeric matrixhaving a microporous structure.
 2. The process of claim 1 wherein saidfabric substrate comprises carboxylic-oxidized regenerated cellulose. 3.The process of claim 2 wherein said fabric substrate comprises fromabout 9 to about 12 percent by weight of said water-solubleoligosaccharides.
 4. The process of claim 1 wherein the weight ratio ofsaid sodium carboxymethyl cellulose to said fabric substrate is fromabout 1:99 to about 20:80.
 5. The process of claim 2 wherein the weightratio of said sodium carboxymethyl cellulose to said fabric substrate isfrom about 3:97 to about 10:90.
 6. The process of claim 1 wherein saidfabric substrate comprises from about 3 to about 20 percent by weight ofwater.
 7. The wound dressing of claim 2 wherein said fabric substratecomprises from about 7 to about 13 percent by weight of water.
 8. Ahemostatic wound dressing made in accordance with the process ofclaim
 1. 9. The wound dressing of claim 8 wherein said fabric substratecomprises carboxylic-oxidized regenerated cellulose.
 10. The wounddressing of claim 9 wherein said fabric substrate comprises from about 9to about 12 percent by weight of said water-soluble oligosaccharides.11. The wound dressing of claim 8 wherein the weight ratio of saidsodium carboxymethyl cellulose to said fabric substrate is from about1:99 to about 20:80.
 12. The wound dressing of claim 9 wherein theweight ratio of said sodium carboxymethyl cellulose to said fabricsubstrate is from about 3:97 to about 10:90.
 13. The wound dressing ofclaim 8 wherein said fabric substrate comprises from about 3 to about 20percent by weight of water.
 14. The wound dressing of claim 9 whereinsaid fabric substrate comprises from about 7 to about 13 percent byweight of water.